#include<iostream>
#include<vector>
#include<string>
using namespace std;

class Solution {
public:
    char findTheDifference(string s, string t) {
        int sumS = 0;
        int sumT = 0;
        for(int i = 0;i<s.size();i++){
            sumS += s[i] - 'a';
            sumT += t[i] - 'a';
        }
        sumT += *(t.end()-1)-'a';
        char c = sumT-sumS + 'a';
        return c;
    }
};

int main(){
    Solution S;
    cout<<S.findTheDifference("abcd","abcde")<<endl;
  
    

}